If you want to execute more than one line at once,
different emacs commands can be used:

You can mark a region in the emacs buffer and
use the emacs menu Blender -> Execute region (Shortcut: C-xC-r)
to execute the region;

You also can move the point into a region delimited by the comment lines
# region-begin and # region-end
and use Blender -> Execute region between `region-begin' and `region-end'
(Shortcut: C-xC-e)
to execute all lines between region-begin and region-end at once.

Installation

You also have to ensure that Dave Love's python mode is installed.
When using Emacs 22 you might consider to reinstall python mode
from
python.el
as the version included in Emacs 22 seems to have some problems
which are fixed in the version mentioned above.
When using Emacs 21 you should install
python-21.el.
For more information see the
PythonMode
page on the
EmacsWiki
and Dave Love's
"Emacs bits" page.